Method and apparatus for corrective secondary saccades analysis with video oculography system

ABSTRACT

A video oculography system for calculation and display of Corrective Secondary Saccades Analysis is disclosed. A method for Objective Diagnostics of at least one of traumatic brain injury, Internuclear Opthalmopligia, Ocular Lateral Pulsion, Progressive Supernuclear Palsy And Glissades comprises the steps of using a VOG system to calculate corrective saccades. The video oculography based system for the subject is configured to collect eye images of the patient in excess of 60 hz and configured to resolve eye movements smaller than at least 3 degrees of motion. The video oculography based system collects eye movement data wherein at least one fixation target is presented to the subject in a defined position configured to yield a voluntary saccadic eye response from at least one eye of the patient. The latency, amplitude, accuracy and velocity of each respective corrective saccade and totals latency and accuracy is calculated.

RELATED APPLICATIONS

The present application claims the benefit of U.S. provisionalapplication Ser. No. 61/102,964 ENTITLED “Method and Apparatus forCorrective Secondary Saccades Analysis with Video Oculography System andMethod for Objective Diagnostics of Internuclear Opthalmopligia, OcularLateral Pulsion, Progressive Supernuclear Palsy and Glissades EyeMovements” filed Oct. 6, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a portable, modular VOG system thatprovides for the calculation and display of saccade eye movement forobjective analysis.

2. Background Information

The present invention relates to Video-oculography, also called VOG, andvideo-oculographic recording of eye movement has been shown to be ahighly effective non-invasive technology for evaluating eye movement.See the Richard E. Gans article in the May 2001, volume 54, pages 40-42of The Hearing Journal, which provide great insight to the beginning ofpractical goggle based VOG systems in 2001. As a historical note, forover 50 years, clinicians and researchers have depended uponelectronystagmography (ENG or EOG) to evaluate peripheral and centralvestibular function. Although ENG/EOG remains in significant use, theneed to place electrodes around the eyes and the inability to record orobserve a torsional nystagmus have represented significant limitationswith this technology. Another drawback is that much of the testing mustbe performed with the patient's eyes closed. Therefore, clinicians andresearchers have been dependent on the graphic, uni-dimensionalrecording to speculate as to what movement the eyes were actually makingbeneath closed eyelids.

Abnormalities of eye movement provide valuable information about thelocation of the dysfunction or disease process. Many abnormalities arespecific to certain pathophysiology or pharmacologic influences. Theadvantage of recording/evaluating eye movements versus other axial orlimb musculature is that they are easier to interpret. Eye movement islimited to movement in three planes: horizontal, vertical, androtational. Pupil dilation represents another parameter that may bedesired to be tracked for certain applications.

Eye movements may be categorized as those that stabilize vision duringhead movement and those that shift vision. The vestibular systemstabilizes vision with head movement through the mechanoreceptors of thelabyrinth, sensing the direction and speed of head acceleration andmoving the eyes accordingly. When disease affects a particularsemicircular canal within the labyrinth, nystagmus may occur in theplane of the involved canal. It is this anatomical and physiologicalrelationship of the VOR that makes new technologic improvements in itsassessment so important.

Current VOG systems that accurately track eye movement for diagnosticpurposes can be represented by those described in U.S. PatentApplication Publications 2005-0099601, 2007-0177103, 2007-0132841,2008-0049186, and 2008-0049187 which are incorporated herein byreference. A further example of a current state of the art VOG systeminclude the 2008 I-Portal® brand VOG systems from Neuro-Kinetics, Inc,which is a fully digital VOG system that delivers accurate 4D eyetracking. The lightweight goggle system is offered in standard 60 Hz andhigh-speed 120 Hz goggle sets, both occluded and free field of view.Higher speeds are available in customized applications with theintegration of higher speed cameras, with the system currentlyaccommodating up to 5000 hz cameras.

A saccade, for the purpose of this application, is a fast movement of aneye. Eye saccades are generally quick, simultaneous movements of botheyes in the same direction. Saccades serve as a mechanism for fixation,rapid eye movement, and the fast phase of optokinetic nystagmus. Humans,and other animals, do not look at a scene in a steady way. Instead, theeyes move around, locating interesting parts of the scene and buildingup a mental ‘map’ corresponding to the scene. One reason for saccades ofthe human eye is that the central part of the retina, the fovea, plays acritical role in resolving objects. By moving the eye so that smallparts of a scene can be sensed with greater resolution, body resourcescan be used more efficiently.

In addition, the human eye is in a constant state of vibration,oscillating back and forth at a rate of about 30-70 Hz. These“micro-saccades” are tiny movements, roughly 20 arcseconds in excursionand are generally imperceptible. They serve to refresh the image beingcast onto the rod cells and cone cells at the back of the eye. Withoutmicrosaccades, staring fixedly at something would cause the vision tocease after a few seconds since rods and cones only respond to a changein luminance.

Saccades are the fastest movements produced by the human body. The peakangular speed of the eye during a saccade reaches up to 1000°/sec inmonkeys and somewhat less in humans. Saccades to an unexpected stimulusnormally take about 200 milliseconds to initiate and then last fromabout 20 to 200 milliseconds, depending on their amplitude. Theamplitude of a saccade is the angular distance that the eye travelsduring the movement. For amplitudes up to about 60 degrees, the velocityof a saccade linearly depends on the amplitude (the so called “saccadicmain sequence”). For instance, an 10° amplitude is associated with avelocity of 300°/sec, and 30° is associated with 500°/sec. In saccadeslarger than 60 degrees, the peak velocity starts to plateau(non-linearly) toward the maximum velocity attainable by the eye.

Saccades may rotate the eyes horizontally or vertically, or in anyoblique direction to change gaze direction (the direction of sight thatcorresponds to the fovea), but normally saccades do not rotate the eyestorsionally. Torsion can be defined as clockwise or counterclockwiserotation around the line of sight when the eye is at its central primaryposition. Head-fixed saccades can have amplitudes of up to 90° (from oneedge of the oculomotor range to the other), but in normal conditionssaccades are far smaller, and any shift of gaze larger than about 20° isaccompanied by a head movement. During such gaze saccades, first the eyeproduces a saccade to get gaze on target, whereas the head follows moreslowly and the vestibulo-ocular reflex causes the eyes to roll back inthe head to keep gaze on the target.

There are many, some rare, abnormalities of eye movements that can bediagnosed through observation of saccades eye movements. See, forreference, Saccade Calibration Testing article by Dr. Timothy C. Hain athttp://www.dizziness-and-balance.com/practice/saccade.htm, whichdiscusses i: Disorders of Saccade velocity (Too slow and Too fast), ii)Disorders of latency (timing), iii) Disorders of Saccades Accuracy(Overshoot, Undershoot, Blindness, Glissades and Pulsion), and iv)Disorders with “Square Wave Jerks” (saccadic oscillations with a latencybetween each saccade). This background is believed to be known to one ofordinary skill in the art associated with the present claimed invention.

Microsaccades are a kind of fixational eye movement. They are small,jerk-like, involuntary eye movements, similar to miniature versions ofvoluntary saccades. They typically occur during prolonged visualfixation (of at least several seconds). Microsaccade amplitudes varyfrom 2 to 120 arcminutes. The role of microsaccades in visual perceptionhas been a debated topic which, currently, is unresolved. It has beenproposed that microsaccades correct displacements in eye positionproduced by drifts, although non-corrective microsaccades also occur.Microsaccades were also believed to prevent the retinal image fromfading, but they do not occur often enough for that purpose, consideringthat perfectly stabilized images can disappear from perception in a fewseconds or less. The current consensus is that all fixational eyemovements are important for the maintenance of visibility.

The present application deals with secondary, and higher order,corrective saccades which may be considered as micro-saccades, namelycorrective micro-saccades, following a main or primary saccade eyemovement.

There remains a need in the art for a simple, and simple to use, VOGsystem effective for clinical and research applications.

SUMMARY OF THE INVENTION

Some of the above objects are achieved with a goggle based VOG systemthat calculates, and displays secondary, and higher, correctivesaccades. An method of measuring ocular response in a subject comprisingthe steps of: A) Providing a video oculography based system for thesubject with the video oculograpghy system configured to collect eyeimages of the patient in excess of 60 hz and configured to resolve eyemovements smaller than at least 3 degrees of motion; B) Collecting eyedata with the video oculography based system wherein at least onefixation target is presented to the subject in a defined positionconfigured to yield a voluntary saccadic eye response from at least oneeye of the patient; and C) Calculating corrective saccade measurementsfrom the eye data including at least one of: i) total number ofcorrective saccades associated with the subject's eye movement to eachfixation target presented to the subject; ii) first corrective saccadelatency associated with the subject's first corrective saccade eyemovement to each fixation target presented to the subject; iii) firstcorrective saccade amplitude associated with the subject's firstcorrective saccade eye movement to each fixation target presented to thesubject; iv) first corrective saccade accuracy associated with thesubject's first corrective saccade eye movement to each fixation targetpresented to the subject; v) first corrective saccade velocityassociated with the subject's first corrective saccade eye movement toeach fixation target presented to the subject; vi) ratio of firstcorrective saccade amplitude to main saccade amplitude associated withthe subject's eye movement to each fixation target presented to thesubject; and vii) ratio of total of corrective saccade amplitudes tomain saccade amplitude associated with the subject's eye movement toeach fixation target presented to the subject. The corrective saccademeasurements can include measurements for a first corrective saccade andat least a second corrective saccade and the corrective saccademeasurements for each corrective saccade includes at least one oflatency, amplitude, accuracy and velocity of each respective correctivesaccade.

This VOG system used in the method of the present invention may providean objective tool for assisting in the diagnosis of ProgressiveSupernuclear Palsy (PSP) and other degenerative cerebellar disordersthat cause highly saccadic results. Some of the above objects areachieved with a goggle based VOG system that objectively calculates, anddisplays main and possibly secondary and higher saccades results toassist in the diagnosis of Internuclear Opthalmoplegia (INO). The systemmay further assist in the diagnosis of Internuclear Opthalmoplegia (INO)for each eye or for bilateral diagnosis. Some of the above objects areachieved with a goggle based VOG system that objectively calculates, anddisplays main and possibly secondary and higher saccades results toassist in the diagnosis of Ocular Lateral Pulsion. Some of the aboveobjects are achieved with a goggle based VOG system that objectivelycalculates, and displays main and possibly secondary and higher saccadesresults to assist in the diagnosis of Glissades eye movements.

These and other advantages of the present invention will be clarified inthe description of the preferred embodiments taken together with theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic views of left and right eye traces ofcollected data for the calculation of corrective saccade measurementsfrom the eye data in a VOG system in accordance with the presentinvention; and

FIGS. 3 and 4 are schematic views of main saccades and a secondarycorrective saccades analysis displays in a VOG system in accordance withthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention uses a portable, head mounted, digital camerabased, video oculography (VOG) system such as the I-Portal® brand VOGsystems from Neuro-Kinetics, Inc (NKI). The I-Portal® brand VOG systemsfrom Neuro-Kinetics, Inc are fully digital VOG systems that deliversaccurate 4D eye tracking recordings. The lightweight goggle system isoffered in standard 60 Hz and high-speed 120 Hz goggle sets in theI-Portal® brand VOG systems, both in occluded and free field of view.Similar VOG systems for implementing the present invention are describedin U.S. Patent Application Publications 2005-0099601, 2007-0132841,2008-0049186, and 2008-0049187 which are incorporated herein byreference in their entirety. The speed and resolution of the cameras maybe further modified in this system with replacement of these digitalcameras with available higher speed digital cameras. The modular natureof the I-Portal® brand VOG system allows this customization to be easilyaccommodated with minimal software accommodations.

The video oculography based system for the subject must be configured tocollect eye images of the patient in excess of (at a minimum) 60 hz andconfigured to resolve eye movements smaller than (at a minimum) at least3 degrees of motion. Increasing the frame rate and resolution improvesthe meaningful data obtained in the present invention particularly whenreviewing higher order corrective saccades. A video oculography basedsystem for the subject configured to collect eye images of the patientin excess of 70 hz and configured to resolve eye movements smaller thanat least 2 degrees of motion should provide meaningful results, whilevideo oculography based system for the subject configured to collect eyeimages of the patient in excess of 75 hz, or even 100 hz and configuredto resolve eye movements smaller than at least 1 degrees of motion isbetter. A video oculography system configured to collect eye images ofthe patient in excess of 200 hz and configured to resolve eye movementssmaller than at least 0.1 degrees of motion is believed to be highlyeffective and easily obtainable through the customizable I-Portal® brandVOG system from NKI.

All of the above identified VOG systems include a goggle head mountedsystem with at least one, and typically two, digital camera(s) trainedon the subjects eyes. Each camera is generally connected to, and mayeven be powered by, a computer, such as through a “firewire” typeconnection. The computer may be a laptop portable computer. The digitalcameras may allow for digital centering of the patient's pupil at leastin one direction through concentrating on the region of interest, andpossibly in two directions (X and Y). The use of digital centeringeliminates the need for a mechanical adjustment mechanism (e.g. a slide)in the given direction.

The VOG system of the present invention is designed to track and record4-D movement of the eye, which is generally movement in an X-Y plane,pupil dilation and eye rotation or torsion about the line of sight. Theconstruction of this type of goggle based VOG system is believed to beknown to one of ordinary skill in the art. The video oculography basedsystem for the subject must be configured to collect eye images of thepatient in excess of 200 hz and configured to resolve eye movementssmaller than (at a minimum) at least 0.1 degrees of motion.

The present invention provides for collecting eye data with the headmounted google based video oculography based system wherein at leastone, and generally a plurality of, fixation target is (are) presented tothe subject, with each target in a defined position configured to yielda voluntary saccadic eye response from at least one eye of the patient.A laser that can project an image anywhere within the users field ofvision (generally +−sixty degrees) is a suitable cost effective andaccurate target generation mechanism. It is critical to know where thetarget is being projected relative to an original eye position. Asuitable target generation mechanism is the Pursuit Tracker® imagecreating device from NKI.

The present invention provides for calculating corrective saccademeasurements from the eye data. The corrective saccade measurements maybe more easily understood with a review of eye traces of such data foundin FIGS. 1 and 2. Line 10 represents the positional eye trace data ofeach eye over time. Over time the trace 10 illustrates a primary saccademovement 12 followed by a first corrective saccade 14 and a secondcorrective saccade 16 prior to reaching a final fixation position 18.Higher secondary saccades (third, forth, etc) 16′ may also be recordedprior to the patients reaching a final fixation position.

Although not shown, it is also possible for a subject to not reach afinal fixation position 18 as shown and the patient can exhibit repeatedunder and over shoot continuing secondary saccade. In such a case thevariability can be noted to the clinician and an average final position18 be used for calculations wherein the average final position iscalculated after the amplitude 54 of subsequent secondary saccades 16′fail to decrease.

The graph of FIG. 1 also shows the positional trace 20 of the laserforming the fixation targets. The trace 20 is rapidly moved, shown at22, to a defined position 24 configured to yield a voluntary saccadiceye response. The trace 20 also illustrates the time 26 of the movementand, more significantly, the amplitude 28 of the movement. The velocityof the laser movement is easily calculated as amplitude 28 divided bytime 26, but this particular velocity is not likely to providemeaningful ocular response information unless the velocity becomes low(which may effect latency measurements). The end of movement 22 marks astart time 13 for the particular fixation target represented at 24.

It is important to note that the traces do not show the direction of themovement 22 from the starting location. The movements 22 will typicallybe performed in vertical movements, both up and down relative to a fixedstarting point, horizontal movements both left and right, andcombinations thereof. Further a combination movement can generate or bebroken down into a pair of responses broken down into vertical andhorizontal components of the target movement and the eye responses.Further it is expected that the starting locations can be throughout theuser's field of vision. As the VOG system can easily accommodate andtrack such distinct movements in differently defined directions, theyare not elaborated further herein, in order to keep this explanationclear and concise. However, it is expected that subjects can exhibitconsiderable directional variations in saccadic response, and suchdirectional differences may be used as objective diagnostic tools.

The trace also shows latency 30 of the primary saccade 12, which is thetime from the start 13 of the fixation target 24 till the beginning ofthe primary saccade 12. This is often referenced as the reaction timefor the eye movement. The primary saccade time 32 represents the time ofthe movement of the eye during the primary saccade 12. The firstcorrective saccade latency 34 is the time from the end of the primarysaccade movement 12 till the beginning of the first corrective saccade14. The first corrective saccade time 36 represents the time of themovement of the eye during the first corrective saccade 14. The secondcorrective saccade latency 38 is the time from the end of the firstcorrective saccade movement 14 till the beginning of the secondcorrective saccade 16. The second corrective saccade time 40 representsthe time of the movement of the eye during the second corrective saccade16. Third and higher order corrective saccade 16′ will include similarlatency and time measurements.

The trace also shows the primary saccade amplitude 50 of the primarysaccade 12, which is a measurement of the magnitude (in degrees) of theeye movement during the primary saccade 12. The trace further shows thefirst corrective saccade magnitude 52 of the first corrective saccade 14and the secondary corrective saccade magnitude 54 of the secondarycorrective saccade 16. Magnitudes of higher order corrective saccades,if present, would also be shown.

The present invention provides a number of objective corrective saccadeanalysis including a total number of corrective saccades associated withthe subject's eye movement to each fixation target presented to thesubject. The total number of corrective saccades for a given fixation issimply the number of corrective saccades until a final position 18 isreached. In the event no actual final position is reached it will be thenumber of corrective saccades until no substantive decrease insubsequent corrective saccade magnitudes is observed.

The present invention provides an objective corrective saccade analysisincluding a first corrective saccade latency 34 and amplitude 52associated with the subject's first corrective saccade eye movement toeach fixation target presented to the subject as described above andshown in the trace.

The present invention provides an objective corrective saccade analysisincluding a second (and higher) corrective saccade latency 38 andamplitude 54 associated with the subject's second (and higher)corrective saccade eye movement to each fixation target 24 presented tothe subject as described above and shown in the trace.

The present invention provides an objective corrective saccade analysisincluding a first corrective saccade accuracy associated with thesubject's first corrective saccade eye movement to each fixation target24 presented to the subject. The first corrective accuracy iseffectively calculated as the total of the primary saccade amplitude 50plus the first corrective saccade amplitude 52 divided by the targetamplitude 28. This accuracy is also a measurement of first correctivesaccade overshoots (accuracy calculations greater than 1) and firstcorrective saccade undershoots (accuracy calculations less than 1).

The present invention provides an objective corrective saccade analysisincluding a first corrective saccade velocity associated with thesubject's first corrective saccade eye movement to each fixation target24 presented to the subject, which is calculated as the first correctivesaccade amplitude 52 divided by the first corrective saccade time 36.

The present invention provides an objective corrective saccade analysisincluding a ratio of first corrective saccade amplitude 52 to mainsaccade amplitude 50 associated with the subject's eye movement to eachfixation target 24 presented to the subject. This can be a weightingfactor or consideration for considering initial latency and totallatency in evaluating reaction time and other parameters of the subject.The present invention provides an objective corrective saccade analysisincluding a ratio of total of corrective saccade amplitudes(52+54+additional, if any) to main saccade amplitude 50 associated withthe subject's eye movement to each fixation target presented to thesubject.

There can obviously be other corrective saccade parameters availablefrom the data obtained in the present invention that researchers andclinicians find useful for particular purposes, such as ratios ofrelative saccadic velocities, ratios of the latencies and the like. Theabove identified parameters are believed to provide objective meaningfuldata from a relatively simple and time efficient testing battery.

The present invention provides an objective corrective saccade analysisincluding wherein the corrective saccade measurements are calculated forthe subjects left and right eyes for each fixation target presented tothe subject. Further, a average corrective saccade measurements arecalculated for each fixation target presented to the subject based uponan average of the left and right eye responses.

FIGS. 3 and 4 represent screenshots of potential graphic and numericaldisplays for the calculated parameters, however a wide variety ofpreferably user adjustable display formats are contemplated. Acombination of graphical and numerical listings of selectable parametersis believed to be most useful.

Another addition to the simple ocular testing shown is to include a userinput device, such as a button or a joystick, in which the user canindicate when the new target is seen by the user. This input would beshown as a line similar to 13 at the point when the input is recorded.This would allow for a mechanical or reflex latency measurement to beeasily added to the available parameters. A joystick would allowdirectional inputs (up, down, left and right) which could be used tominimize anticipatory inputs as the direction of the joystick inputwould need to match the direction of the target 24 from the start for avalid reflex input. Comparing the reflex latency to the ocular reflextime is a further useful tool to researchers and clinicians

Traumatic Brain Injury (TBI)

Objective measurement of Traumatic Brain Injuries (TBI), such asconcussions, is not readily available to researchers or clinicians. Thecorrective saccade parameters that are provided with the method andapparatus of the present invention are believed to assist in formingobjective indicators of TBI.

First, subjects that have a pre-TBI baseline under the present inventioncan use these results to test later to see if there is a potential forTBI due to intervening injury or trauma. Substantial variation in asubjects results from a their own baseline results for total number ofcorrective saccades, first corrective saccade latency, first correctivesaccade amplitude, first corrective saccade accuracy associated with thesubject's first corrective saccade eye movement to each fixation targetpresented to the subject, first corrective saccade velocity, ratio offirst corrective saccade amplitude to main saccade amplitude, or ratioof total of corrective saccade amplitudes to main saccade amplitudecould be used as TBI indicators, individually, or more likelycollectively.

However it is anticipated that a normative database of correctivesaccade parameters for the relevant populations (e.g. high schoolathletes) could be used to form an “aggregate baseline” and a subjectspost trauma results compared to the aggregate base line to determine ifTBI is seen as likely or a possibility, even if the patient were neverpreviously tested.

Internuclear Opthalmoplegia (INO)

Internuclear ophthalmoplegia (INO) is a disorder of conjugate lateralgaze in which the affected eye shows impairment of adduction. Thedisorder is caused by injury or dysfunction in the medial longitudinalfasciculus (MLF), a heavily-myelinated tract that allows conjugate eyemovement. In young patients with bilateral INO, Multiple Sclerosis oftenthe cause. In older patients with one-sided lesions a stroke is adistinct possibility. However, there is a long list of possible causes.Currently, audiologists are diagnosing INO through direct observation ofthe patient or of a recording of the patient (i.e. a trace of eyeposition.

In the VOG system of the present invention an objective measure ofpatient corrective saccadic response is obtained to provide an objectivetool for INO diagnosis in patients. Namely the saccades eye movements ofthe patient are calculated for each eye, including the calculation ofthe main saccades and secondary corrective saccades. The details of theanalysis are described in connection with FIGS. 1-2. The saccadescalculations include calculations for over and under shoots, latency,accuracy, velocity, and comparison of such values to the other eyeresults in bilateral calculations. The subsequent corrective saccadesfollowing the secondary are similarly calculated.

With regard to the diagnosis of INO these objective measurements providean objective tool for such diagnosis. Comparison of the main saccadesmeasurements, and possibly the secondary and higher corrective saccade,to threshold measurements relative to the target and the other eyeresponse will provide indication of INO diagnosis. The particularthresholds established may vary with age and other physiologicparameters of the patients as will be understood by those of ordinaryskill in the art. The calculation of the INO diagnosis may includeranges of results for the patients, such as a result of “INO highlylikely”, “INO possible” and “INO not indicated”. Alternatively anumerical scaled result can be given on a preset scale to give numericalresults as desired.

Ocular Lateral Pulsion (OLP)

Ocular Lateral Pulsion (OLP) is caused by infarcts in the distributionof the posterior inferior cerebellar artery or distribution of thesuperior cerebellar artery. With regard to the diagnosis of OLP theobjective saccade eye movement of a goggle based VOG system provide anobjective tool for diagnosis of OLP.

Comparison of the main saccades measurements, and possibly the secondaryand higher corrective saccade, to threshold measurements relative to thetarget and the other eye response will provide indication of OLPdiagnosis. The particular thresholds established may vary with age andother physiologic parameters of the patients as will be understood bythose of ordinary skill in the art. The calculation of the OLP diagnosismay include ranges of results for the patients, such as a result of “OLPhighly likely”, “OLP possible” and “OLP not indicated”. Alternatively anumerical scaled result can be given on a preset scale to give numericalresults as desired.

Glissades Eye Movements

Glissades eye movements are when eye velocity slows just prior toreaching the eye target and the eye gradually acquires the target orsteps with a small additional saccade. Glissades eye movements can becaused by a cerebellar disorder, eye muscle or nerve weakness or headmovement during the test. Current diagnosis is through visual inspectionof patient eye response. With regard to the diagnosis of glissades eyemovement the objective saccade eye movement of a goggle based VOG systemprovide an objective tool for diagnosis of glissades eye movement.

Comparison of the main saccades measurements, and possibly the secondaryand higher corrective saccade, to threshold measurements relative to thetarget and the other eye response will provide indication of glissadeseye movement diagnosis. The particular thresholds established may varywith age and other physiologic parameters of the patients as will beunderstood by those of ordinary skill in the art. The calculation of theglissades eye movement diagnosis may include ranges of results for thepatients, such as a result of “glissades eye movement highly likely”,“glissades eye movement possible” and “glissades eye movement notindicated”. Alternatively a numerical scaled result can be given on apreset scale to give numerical results as desired.

Progressive Supernuclear Palsy

Additionally the measurement and display of secondary, and higher,corrective saccades may further include objective diagnosis ofassociated diseases for the secondary saccades may be indicative. Theseinclude Progressive Supernuclear Palsy (PSP) and other degenerativecerebellar disorders that cause highly saccadic results.

Progressive supranuclear palsy (PSP) is a rare brain disorder thatcauses serious and permanent problems with control of gait and balance.The most obvious sign of the disease is an inability to aim the eyesproperly, which occurs because of lesions in the area of the brain thatcoordinates eye movements. Some patients describe this effect as ablurring. PSP patients often show alterations of mood and behavior,including depression and apathy as well as progressive mild dementia.Initial complaints in PSP are typically vague and an early diagnosis isalways difficult. PSP is often misdiagnosed because some of its symptomsare very much like those of Parkinson's disease, Alzheimer's disease,and more rare neurodegenerative disorders, such as Creutzfeldt-Jakobdisease. In fact, PSP is most often misdiagnosed as Parkinson's diseaseearly in the course of the illness. Memory problems and personalitychanges may also lead a physician to mistake PSP for depression, or evenattribute symptoms to some form of dementia. The key to diagnosing PSPis identifying early gait instability and difficulty moving the eyes,the hallmark of the disease, as well as ruling out other similardisorders, some of which are treatable. The present invention cangreatly improve proper and early PSP diagnosis.

Similar to the above diagnostic tools, comparison of the main saccadesmeasurements, and generally the secondary and possibly higher correctivesaccades, to threshold measurements relative to the target and the othereye response will provide indication of PSP diagnosis. The particularthresholds established may vary with age and other physiologicparameters of the patients as will be understood by those of ordinaryskill in the art. The calculation of the PSP diagnosis may includeranges of results for the patients, such as a result of “PSP highlylikely”, “PSP possible” and “PSP not indicated”. Alternatively anumerical scaled result can be given on a preset scale to give numericalresults as desired.

In short the present invention provides a tool for clinicians,researchers, caregivers, and educators (and even manufacturers) that canbe used in a number of distinct applications and although the presentinvention has been described with particularity herein, the scope of thepresent invention is not limited to the specific embodiment disclosed.It will be apparent to those of ordinary skill in the art that variousmodifications may be made to the present invention without departingfrom the spirit and scope thereof. The scope of the invention is not tobe limited by the illustrative examples described above.

What is claimed is:
 1. A method of measuring ocular response in asubject comprising the steps of: Providing a video oculography basedsystem for the subject with the video oculography system configured tocollect eye images of the patient in excess of 60 hz and configured toresolve eye movements smaller than at least 3 degrees of motion;Collecting eye data with the video oculography based system wherein atleast one fixation target is presented to the subject in a definedposition configured to yield a voluntary saccadic eye response from atleast one eye of the patient, wherein the initial saccadic eye responseto the target is a primary saccadic response and subsequent saccadic eyeresponses to the target are corrective saccadic eye responses to thetarget; Calculating corrective saccade measurements from the eye dataincluding at least one of: i) total number of corrective saccadesassociated with the subject's eye movement to each fixation targetpresented to the subject; ii) first corrective saccade latencyassociated with the subject's first corrective saccade eye movement toeach fixation target presented to the subject; iii) first correctivesaccade amplitude associated with the subject's first corrective saccadeeye movement to each fixation target presented to the subject; iv) firstcorrective saccade accuracy associated with the subject's firstcorrective saccade eye movement to each fixation target presented to thesubject; v) first corrective saccade velocity associated with thesubject's first corrective saccade eye movement to each fixation targetpresented to the subject; vi) ratio of first corrective saccadeamplitude to a primary saccade amplitude associated with the subject'seye movement to each fixation target presented to the subject; and vii)ratio of total of corrective saccade amplitudes to the primary saccadeamplitude associated with the subject's eye movement to each fixationtarget presented to the subject.
 2. The method of measuring ocularresponse in a subject according to claim 1 wherein the video oculographysystem configured to collect eye images of the patient in excess of 70hz and configured to resolve eye movements smaller than at least 2degrees of motion.
 3. The method of measuring ocular response in asubject according to claim 1 wherein the video oculography systemconfigured to collect eye images of the patient in excess of 100 hz andconfigured to resolve eye movements smaller than at least 1 degrees ofmotion.
 4. The method of measuring ocular response in a subjectaccording to claim 1 wherein the video oculography system configured tocollect eye images of the patient in excess of 200 hz and configured toresolve eye movements smaller than at least 0.1 degrees of motion. 5.The method of measuring ocular response in a subject according to claim1 wherein the corrective saccade measurements are calculated for thesubjects left and right eyes for each fixation target presented to thesubject.
 6. The method of measuring ocular response in a subjectaccording to claim 5 wherein average corrective saccade measurements arecalculated for each fixation target presented to the subject based uponan average of the left and right eye responses.
 7. The method ofmeasuring ocular response in a subject according to claim 1 furthercomprising the step of displaying the collected eye data from eachfixation target as an eye movement trace graphing angular movement ofthe subject eye over time relative to the position of the fixationtarget.
 8. The method of measuring ocular response in a subjectaccording to claim 1 wherein the corrective saccade measurements includemeasurements for a first corrective saccade and at least a secondcorrective saccade and the corrective saccade measurements for eachcorrective saccade includes at least one of latency, amplitude, accuracyand velocity of each respective corrective saccade.
 9. The method ofmeasuring ocular response in a subject according to claim 1 wherein thevideo oculography based system is a head mounted system configured tocollect eye images of the patient in excess of 75 hz and configured toresolve eye movements smaller than at least 1 degrees of motion, andeach fixation light is a laser configured to display a visible target atany point in the patients field of vision.
 10. The method of measuringocular response in a subject according to claim 1 wherein the videooculography based system wherein the corrective saccade measurementsfrom the eye data is used as an objective diagnostic tool for at leastone of traumatic brain injury, Internuclear Opthalmopligia, OcularLateral Pulsion, and Progressive Supernuclear Palsy And Glissades.